Is COPD a Risk Factor for Lung Cancer?

Chronic obstructive respiratory disease (COPD) is considered an independent risk factor for lung cancer in more ways than one. Not only is tobacco smoking the number one risk factor for both diseases, but even never-smokers who develop COPD are far more likely to develop lung cancer than those who don't.

How COPD triggers the onset of lung cancer is not entirely clear, but, as a group of progressive obstructive diseases—which includes chronic bronchitis and emphysema)—COPD is known to cause profound and irreversible changes to the airways. It is not entirely surprising, therefore, that COPD is most commonly linked to squamous cell carcinoma, the type of cancer that develops in the airways.

How COPD and Lung Cancer Are Connected

There are dozen of studies that have linked COPD to lung cancer. Excluding all other risk factors, COPD appears to double the risk of lung cancer compared to people who do not have COPD. Among smokers with COPD, the risk is increased five-fold. All told, around 1% of people with COPD will develop lung cancer each year, most commonly squamous cell carcinoma.

The two diseases are also linked by the timing of their appearance, which almost invariably increases with age. COPD principally affects smokers over 40 and is 2.5 times more likely to occur in people over 60. This dovetails with the onset of lung cancer, which most commonly affects smokers (both current and former) by age 70.

According to a 2018 review in the International Journal of Chronic Obstructive Pulmonary Disease, between 40% and 70% of people with lung cancer have co-existing COPD. This includes people who have not been diagnosed with COPD but have evidence of obstruction based on pulmonary function tests.

The similarities between the two diseases are perhaps best highlighted in a 2012 review of studies published in the European Respiratory Journal:

  COPD Lung Cancer
Main risk factor Smoking Smoking
Ages affected (generally) 50-80 65+
Rank, common causes of death 4th 7th
% smokers developing in lifetime 10% to 15% 10% to 15%
Increased risk due to >20 pack-year history 450% 300%
Effect of quitting (>10 years) 65% reduced severity 50% to 75% reduced risk

Theories Behind the Link

There are many theories as to why COPD increases the risk of lung cancer. It is believed that multiple factors contribute, including genetics, environment, and lifestyle.

Genetics

One theory is that there are genetic abnormalities common to both COPD and lung cancer. The overlapping genetic susceptibility is believed to make some people more likely to develop both diseases.

Scientists have identified a number of gene mutations commonly seen in people with COPD and lung cancer. These mainly occur on chromosome 6 and include mutations of the CHRNA3, CHRNA5, FAM13A, HHIP, HTR4, and VEGFR1 genes.

Nicotine addiction is also linked to commonly shared genetic mutations.

DNA methylation, a process in which the function of a gene is changed even if the genetic structure is intact, is also seen with COPD and lung cancer. DNA methylation is known to promote lung inflammation in people with COPD while inhibiting tumor suppressor genes that regulate cell division and repair damaged cells.

DNA methylation is known to affect two genes linked to both COPD and lung cancer: CCDC37 and MAP1B.

Cilia Damage

Another theory is that the destruction of cilia in the airways exposes the lungs to higher concentrations of carcinogenic (cancer-causing) substances from cigarettes and environmental pollution.

Cilia are tiny hair-like structures in the lining of the airways that brush toxins toward the trachea (windpipe) and mouth to be expelled. Cigarette smoke effectively paralyzes these structures and causes them to flatten out over time.

With COPD, the persistent inflammation can cause irreversible widening and stiffening of the airways, known as bronchiectasis. When this occurs, the cilia meant to protect the lungs are all but destroyed. This allows the roughly 70 carcinogens found in cigarette smoke unimpeded access to the smaller airways and air sacs of the lungs.

Pulmonary Inflammation

Yet another theory is that chronic inflammation triggered by COPD places oxidative stress on airway tissues. Oxidative stress is essentially an imbalance between the production of free radicals that cause harm to DNA and antioxidants meant to neutralize them and keep cells healthy.

When oxidative stress is increased, the ability of DNA to synthesize proteins can be severely impaired, leading to the formation of abnormal cells. Oxidative stress caused by COPD can also damage telomeres (the structures at the end of chromosomes that tell cells when to die).

If both of these things occur, not only can cancer cells develop, but they will effectively become "immortal," replicating and invading tissues without end.

What to Do If You Have COPD

If you have COPD, talk to your doctor about the risk of lung cancer. Because the two diseases share common risk factors, there will be things you can do to significantly reduce your risk of cancer while reducing the severity and frequency of COPD symptoms.

Quit Smoking

No matter how many years you have smoked, it is never too late to stop. A 2018 study from Vanderbilt University Medical Center found that quitting cigarettes for five years decreases the risk of cancer by no less than 39%.

Many smoking cessation aids are provided free of charge under the Affordable Care Act, allowing you multiple quit attempts per year without having to pay a cent. Secondhand smoke should also be avoided.

Take COPD Treatments as Prescribed

COPD medications, when used properly, reduce the severity and frequency of attacks while tempering the underlying inflammation that drives the disease. However, only around 33% of people on COPD medications are fully adherent.

There is increasing evidence that the daily use of a high-dose inhaled corticosteroid can protect against lung cancer in people with COPD, further bolstering the need for uninterrupted therapy.

Check Your Home for Radon

Radon, an odorless, colorless gas emitted from the breakdown of uranium in soil, is the leading cause of lung cancer in people who have never smoked. If you have COPD, the risk of radon exposure is increased.

To reduce your risk, buy an inexpensive radon home test at a local hardware store, and contact contractors in your area about radon mitigation if the readings are high.

Get Screened

If you have COPD and a history of smoking, you may be eligible for annual lung cancer screening. The test, involving a low-dose CT scan of the chest, can reduce the risk of death from lung cancer by as much as 20%.

The test is intended for older adults who are heavy smokers. It is less useful in younger adults or those who are not at high risk of lung cancer.

Guidelines for Lung Cancer Screening

Currently, the U.S. Preventive Services Task Force recommends annual lung cancer screening in people who meet all of the following criteria:

  • Are between the ages of 50 and 80
  • Have a 20-pack history of smoking or greater
  • Continue to smoke or have quit in the past 15 years

A Word From Verywell

If you have COPD, it is important to be aware of your increased risk of lung cancer. This is true whether you currently smoke, smoked in the past, or have never smoked a cigarette in your life.

Because most lung cancers are diagnosed in the advanced stages when they are less treatable, the most important thing you can do is to remain linked to medical care, ideally a qualified pulmonologist. Even if you aren't eligible for lung cancer screening, the routine monitoring of your lungs and lung function can often provide clues as to the onset of lung cancer.

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